This invention relates to a process for preparation of polyphenylene oxides using chelate compounds.
There are a number of known methods of preparing polyphenylene oxides using metal chelate compounds. One example is a method using a catalyst comprising a manganese, cobalt or copper salt and an alkali metal alcoholate or phenolate, such as disclosed in Belgian Pat. No. 712,845. Another example is a method employing a catalyst comprising a manganese salt, an alcohol and a tertiary amine, such as disclosed in Belgian Pat. No. 710,263. A further example is a method using a basic cupric salt, such as disclosed in Japanese Patent Publication No. 18692/61. A still further example is a method using a cobalt (II) chelate compound represented by the Registered Trademark "Salcomine", which is disclosed in Japanese Patent Publication No. 22154/70. The "Salcomine" is a chelate compound composed of a condensate of two molecules of salicyl aldehyde with one molecule of ethylene diamine[N,N'-ethylenebis(salicylidene imine)]and cobalt (II). It is known that this compound absorbs and liberates oxygen reversibly.
As is shown in the Comparative Examples given below, these known methods are defective and leave much to be desired. They have low reaction rates. Thus, to obtain a polymer having a high degree of polymerization, the reaction must be conducted for a long period of time. From a commercial point of view this is unacceptable. The productivity and hence cost would be adversely affected.
The method using a basic cupric salt has numerous disadvantages. For example, a large quantity of aniamine must be used. Moreover, diphenoquinone is readily formed as a by-product. Also, the catalyst is deactivated by water formed by the reaction. Furthermore, coloration is caused to occur by the amine remaining in the resulting polymer.
Furthermore, when using the "Salcomine" catalyst, it is difficult to maintain the quality of the catalyst at a uniform level, although the same synthesis method is used. Therefore, the method using this "Salcomine" catalyst does not readily produce polymers having uniform quality, because of the relatively large degree of uneveness in the activity of the catalyst.